The mayor plans to make a statement next week explaining support for the measure, aimed at preventing cuts at the LAPD and other agencies.

Los Angeles Mayor Antonio Villaraigosa on Friday backed the half-cent sales tax hike on the March 5 ballot, which is being pushed as a way to shield the Police Department and other public safety agencies from employee cuts.

The increase, which is backed by some key business leaders and labor leaders as a means to preserve public services, would push the city's sales tax rate to 9.5%, among the highest in the state.

Villaraigosa did not give his reasons for backing Proposition A, saying through a spokesman that he would make a statement next week. A day earlier, the city's top budget analyst warned that a defeat of the measure, which would generate nearly enough to erase a $216-million budget shortfall, could require cutting at least 500 police officers.

That would largely undo one of Villaraigosa's signature accomplishments during his two terms in office: adding 800 officers to the LAPD, despite a major recession.

Mayoral candidate Kevin James, who opposes the tax increase, said it would hurt the city's economy. He also questioned Villaraigosa's insistence on keeping LAPD staffing at 10,000 officers.

"It's not about any magic number. It's about the number of officers out in the community. And when we have so many officers behind the desk because of outdated technology and outdated policies, that's where the failed leadership is," he said.

Villaraigosa spokesman Peter Sanders declined to respond, but noted in an email that the city's crime rates are "at their lowest since the 1950s."

If Proposition A passes, Villaraigosa will conclude his time in office with a sales tax increase focused on public safety — an idea he fiercely denounced the year he became mayor.

In 2005, Villaraigosa — then seeking to unseat Mayor James Hahn — blocked Hahn's effort to place a sales tax increase on the ballot to pay for 1,000 more officers. That vote came at a time of intense debate over how to pay for an expansion of the LAPD.

Villaraigosa promised to find another way to pay for 1,000 additional officers and succeed where Hahn failed.

As mayor, Villaraigosa convinced the City Council to triple the trash fee for homeowners from $11 to $36.32 per month, saying that the proceeds would pay for more police. Once the budget crisis hit, however, the city found that it did not have enough money for both the police buildup and other programs.

Thousands of positions in other departments were reduced as the hiring of additional officers continued.

Villaraigosa previously said he would not support the tax unless the City Council took steps to ensure that the number of police officers would not be reduced. He also demanded that the council eliminate 209 civilian positions, a majority of them in the LAPD.

City Administrative Officer Miguel Santana said Friday that those positions no longer exist.